trout

i’ve reentered the nightmare

when i last left off this project in ~september, I basically hit a wall with optimizations. I had a crapload of pruning and whatnot, but the elo of the engine didn’t really reflect it. I then did a search rewrite but got stuck on RFP (reverse futility pruning), which is supposed to gain a lot of strength but did basically nothing for me.

brief (??) aside: reverse futility pruning, in simple terms, checks if the static evaluation (evaluation without searching moves) is above beta (if a move scores above beta, it’s “too good,” and the opponent won’t allow that position to happen in the first place) by some margin. if it is, it’ll return without searching any moves, because it’s not likely that the player can lose that much material/positional advantage in whatever depth is left to search.

anyway, i’m still stuck on this. I’ve re-reimplemented half the search to recheck its correctness, because correctness issues can sometimes stuff new optimizations, but it seems to be all good. RFP still doesn’t do jack.

i don’t really know where to go from here. I could just ignore it, but the fact that RFP doesn’t do anything (for reference, another engine dev i talked to got like 80 elo out of RFP, which is insane) is a troubling sign and might mean something else is wrong.

hello! trout again. i’m gonna try to get this to #1 haskell engine, but it’s been such a pain…

after summer of making I did some more work on this, but hit a wall where all my changes either did nothing or gained like 10elo (which is not enough for the hundreds i need). I tried rewriting part of search but hit a wall again with the same problem, on features that should have made improvements!

i’ve been fighting with the search some more trying to get reverse futility pruning to do something meaningful. in someone else’s engine, it gained i think 80+ elo in total (!!!), which is bonkers compared to the 20 or something i get on a good day. it’s not a good day, so RFP actually manages to lose elo here.

i might have to rewrite search again. i don’t know how much of this is just wrong.

(here’s the commented out old search)